Transportation in Animals and Plants Class 7 Notes Science Chapter 7

Every living thing, including animals and plants, needs food, water, and oxygen to stay alive. But how do these important substances move around in their bodies? And how do animals get rid of waste? The heart and blood vessels play a big role in this process, working together as the circulatory system. In this chapter, we will explore how substances are transported within animals and plants, helping them survive and stay healthy.

Circulatory System

The circulatory system is like the body's transportation network. It carries important substances like oxygen, nutrients and water to every part of the body. It also helps remove waste products. 

The circulatory system is made up of the heart, blood, and blood vessels.

Circulatory System

Blood

Blood is a fluid in the body that plays a key role in the circulatory system. It is responsible for transporting oxygen from lungs to the cells throughout the body.  It also carries waste products, like carbon dioxide, away from the cells. This process allows waste products to be removed from the body. 

• Blood consists of:
  • Plasma: The liquid part of blood that carries the cells.
  • Red Blood Cells (RBCs): These cells carry oxygen from the lungs to the rest of the body and bring carbon dioxide back to the lungs to be exhaled. It has iron containing red-colored pigment called hemoglobin that combines with oxygen and transports it to all parts of the body. The presence of hemoglobin gives red color to blood.
  • White Blood Cells (WBCs): These cells help fight infections and protect the body from harmful bacteria and viruses.
  • Platelets: These tiny cell fragments help in blood clotting, which stops bleeding when you get a cut. When the platelet count decreases, excessive bleeding takes place and may even cause death.

Blood Vessels

Blood flows through narrow pipe-like structures in the body, known as blood vessels. These blood vessels transport food, oxygen and waste within the body.

• Different types of blood vessels transport important things like oxygen.
• When we breathe in, oxygen fills our lungs.
• This oxygen needs to be delivered to every part of the body.
• Blood vessels called arteries carry oxygen-rich blood from the heart to the rest of the body.
• Arteries have thick and stretchy walls because the blood inside them moves very fast and under a lot of pressure.

Arteries - These blood vessels carry oxygen-rich blood away from the heart to the rest of the body. 

Blood Vessel

• The pulse is the throbbing you feel when you place your fingers on certain parts of your body, like your wrist or neck.
• This throbbing happens because your heart is pumping blood through your arteries.
• The pulse is the result of that blood moving through the vessels.
• The pulse rate is the number of times you feel the pulse in one minute.
• It tells you how fast your heart is beating.
• For most people who are resting, the pulse rate is usually between 72 and 80 beats per minute.
• Your pulse rate can change depending on your activity level, emotions, or overall health.

Veins - It carry blood that is low in oxygen and full of waste products back to the heart.

• Blood moves through the body and collects waste materials like carbon dioxide from the cells.
• This used blood needs to return to the heart to be sent to the lungs.
• In the lungs, carbon dioxide is removed when we breathe out.
• Veins are the blood vessels that carry this blood back to the heart.
• Pulmonary artery carries blood from the heart. It carries carbon dioxide-rich blood to the lungs. Pulmonary vein carries oxygen-rich blood from the lungs to the heart.

Capillaries are extremely thin blood vessels that form a network between the arteries and veins. When arteries reach the tissues, they divide into these tiny capillaries.  The capillaries come together to create veins. These veins then carry blood back to the heart. 

Difference between vein and Artery

Heart

The heart is an organ that acts like a pump for your body. Its main job is to keep blood moving through your blood vessels, making sure that oxygen and nutrients reach every part of your body.

Location and Size: The heart is located in the chest, slightly to the left side. The size of your fist 

Structure : The heart has four chambers to prevent the mixing of oxygen-rich blood and carbon dioxide-rich blood. The two upper chambers are called atria (singular: atrium), and the two lower chambers are called ventricles. 

Wall between these two helps to it ensures that blood rich in oxygen do not mix with the blood rich in carbon dioxide. 

These arrows in the above figure show the direction of the blood flow from the heart to the lungs and back to the heart from where it is pumped to the rest of the body.

Heartbeat

A heartbeat is the sound and rhythm made by your heart as it pumps blood through your body.

• The walls of the heart are made up of the most powerful muscles. 
• Their rhythmic contraction and relaxation constitute heartbeats.
• Heartbeat can be recognised by placing the palm on the left side of the chest.
• The device that amplifies the sound of a person's heartbeat is called a stethoscope and consists of a chest piece that holds a sensitive diaphragm.
• The pressure applied by blood on the walls of an artery at a particular part is the pulse. The number of times the heart beats in a minute is the same as the pulse rate.
• The best place to check pulse rate is the wrist. The ideal pulse rate is 70 to 80 per minute. 

• The regular beating of the heart's chambers keeps blood moving and helps transport important substances to different parts of the body.

  Are you curious to know whether animals like sponges and Hydra have blood? 

  • These animals don't have a circulatory system like we do.
  • They live in water, which brings food and oxygen into their bodies.
  • The water also removes waste materials and carbon dioxide as it flows out.
  • Because of this, sponges and Hydra don't need blood to move things around in their bodies.

Excretion in Animals

The cells in the body perform various activities. Waste products such as urea, uric acid and excess water are formed and have to be removed from the body. The process of the removal of waste produced in the cells in living organisms is called excretion. The organs that help in the process of excretion constitute the excretory system. 

Excretory Products in Animals

• Aquatic animals like fishes excrete ammonia, which dissolves directly in water.
• Some terrestrial animals such as birds, lizards, and snakes excrete a semi-solid, white compound known as uric acid.
• Humans primarily excrete urea as their major excretory product.

Excretory System in Humans 

• The excretory system in humans is essential for keeping the body healthy by removing waste and extra substances from the blood.
• Blood is filtered in the kidneys using tiny blood vessels known as capillaries.
• As blood moves through these capillaries, it removes waste materials like urea, extra salts, and toxins.
• When the blood reaches the two kidneys, it contains both useful and harmful substances. The useful substances are absorbed back into the blood. 
• The waste and extra substances that are filtered out mix with water to create urine.
• This urine travels from the kidneys through tubes called ureters to the urinary bladder.
• The urinary bladder acts as a temporary storage for urine.
• As the bladder fills with urine, its walls stretch, which signals that it’s time to go to the bathroom.
• When the bladder is full, urine is pushed out of the body through the urethra, a muscular tube connecting the bladder to the outside.
• On average, an adult passes about 1 to 1.8 liters of urine every 24 hours.
• The makeup of urine can change, but it usually contains around: 95%water, 2.5%urea, 2.5% other waste products

Excretory System

Note: The functioning of the kidneys stops when there is an infection. This is known as kidney failure. 

As a result, waste products remain in the blood. When blood is not filtered, survival becomes difficult, so it is filtered through an artificial kidney. The process is called Dialysis. The artificial kidney is called a dialysis machine.

Sweating and it's purpose

• Sweat consists of water and salts. In summer, white patches can form on clothes, notably in areas like underarms, due to salts present in sweat.
• Sweat serves another purpose. Similar to how water evaporating from the pores of an earthen pot (matka) cools the pot, sweat evaporating from our skin helps in cooling our bodies.

Transport of Substances in Plants

Plants make their own food by taking in carbon dioxide from the air, minerals and water from the soil. They release oxygen and water vapour and the process is termed Photosynthesis. Plants get energy from the food to perform vital activities. Food and water are transported to various cells in the body.

Photosynthesis equation

Transportation Process

Transport of Water and Minerals

• Plants take in water and minerals through their roots, aided by tiny structures called root hairs.
• These microscopic structures greatly expand the surface area of the roots, allowing for better absorption of water and vital nutrients dissolved in it.
• Root hairs come into direct contact with the water found between soil particles.
• Plants have special pipe-like vessels made up of specific cells, which together create the vascular tissue known as xylem.
• The xylem is responsible for transporting water and nutrients from the soil to different parts of the plant.
• It forms a continuous network of channels that connect the roots to the leaves through the stem and branches, ensuring water is distributed throughout the plant.
• Water and minerals move all around the plant, just like food does.
• Another part of the plant, called phloem, helps carry the food produced by the plant to all its parts.
• Both the xylem and phloem are essential for transporting the resources that keep the plant healthy and growing.

Transpiration

Transpiration is when plants release water vapor into the air through tiny openings on their leaves called stomata. It's like the plant is sweating to cool down and get rid of extra water.

• By the force of suction, water and nutrients are transported to all parts of a plant.
• Water and minerals reach the leaves and use only a small amount to make food.
• There are small pores, called stomata, on the lower surface of the leaves through which excess water is released in the form of water vapour.
• Transpiration increases the moisture content of the atmosphere, thus bringing about a cooling effect in the immediate surroundings.
• Suction develops in the plant when water from the leaves is lost in the form of water vapour.
• This force is used to absorb more water and minerals.
• The suction force is also known as the transpiration pull.
• It is strong enough to draw water even in tall trees.

We learned how animals use their circulatory system to move blood, nutrients, and wastes. Plants use xylem and phloem to transport water, nutrients, and food. These systems are vital for the survival and function of all living organisms.